Seat assembly

ABSTRACT

A seating assembly including a base having a bottom ring supported by casters, a pan supported by the bottom ring, a central hub forming an upwardly opening cavity, a plurality of legs extending outward and downward from the central hub to the bottom ring, a one-piece molded seat shell, a mounting bracket forming four apertures and including a female connector and at least one rib member that extends downward adjacent the female connector, the at least one rib member including end edges that forms first and second stop surfaces, the mounting bracket attached to the bottom of the seat by passing fasteners through the apertures, a support arm, a mounting assembly including, a cup member, a base tube, an annular mounting collar and a pivot cover forming an upwardly opening annular channel and an inverted U-shaped opening, the pivot cover attached to the mounting collar with the first end of the support arm extending through the inverted U-shaped opening and the at least one rib member received within the annular channel.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of pending U.S. patent applicationSer. No. 14/179,888 which was filed on Feb. 13, 2014 which was titled“Node Seat To Base Mounting Assembly” which is a continuation of andclaims priority to U.S. patent application Ser. No. 14/104,473 which wasfiled on Dec. 12, 2013 which is titled “Node Seat To Base MountingAssembly” which is a continuation of and claims priority to U.S. Pat.No. 8,696,056 that was filed on Jan. 10, 2011, that issued on Apr. 15,2014 titled “Seating Unit” which claims priority to U.S. ProvisionalPatent Application Ser. No. 61/300,298 filed on Feb. 1, 2010 titled“Seating Unit”, each of which are incorporated by reference herein.

BACKGROUND OF THE INVENTION

The present invention relates to a movable seating unit including anoptional tablet assembly. More particularly, the present inventionrelates to a seating unit having a seat structure freely rotatable on abase, and optionally a tablet assembly. The tablet assembly includes atablet which rotates on the end of a support arm and the support armwhich rotates around the center shaft of the seating unit. The presentinvention also relates to a seating unit having a stable, mobile basewith storage capability.

The need for learning is a fundamental rule of business, and a criticalelement of success. In an information age, effective, technology-drivenlearning is required not only in school, but also on the job. In part,effective learning depends on an environment which promotes interactionand collaboration with other students or coworkers and accommodates theuse of multimedia technology. As new interactive technologies andmultimedia training programs emerge, the use of seating designed tosupport the necessary amount of collaboration and self-direction isimportant.

Traditional classrooms, lecture halls, auditoriums, and meeting roomsoften provide comfortable seating which allows students and employees toconcentrate and take notes. However, traditional seating options are notsufficiently flexible to adapt to a variety of seating arrangementswhich foster interactions required for group learning. Typically,traditional seating options also do not provide storage and easy accessto personal belongings. Whether it is a backpack, computer, briefcase orpurse, in a dynamic learning environment, persons want their belongingsto accompany them and be readily accessible. Seating must also provide arange of postural choices and accommodate persons of different sizes.Optionally, seating which promotes interaction and collaboration mustalso provide a worksurface that can be positioned in a variety of waysand is large enough for electronic devices such as a laptop computer.

At the same time, seating must be economical. In today's economy, bothschools and companies must work within a limited budget. Thus, a lowcost seating unit which provides comfort, convenience, durability andflexibility in learning and collaborating environments is desired.

BRIEF SUMMARY OF THE INVENTION

In one embodiment of the present invention, a seating unit includes atablet assembly including a support arm attached at one end to theseating structure. A second end of the support arm includes a projectionand is attached to a pivot assembly. The pivot assembly includes atablet mount having a connecting portion, a bushing having a rib and anadjacent cutout, and an inner tube. The bushing is inserted into thesupport arm second end such that the projection protrudes through thecutout. The bottom of the inner tube is inserted into the bushing andthe top of the inner tube is inserted into the connecting portion.

In another embodiment of the present invention, a seating unit includesa seat structure, a base and a tablet assembly mounted between the seatstructure and the base. The seat structure includes a mounting brackethaving a female connector. The tablet assembly includes a support armhaving a mounting collar on one end. The base includes a base supportand a base mounting assembly having a cup attached to the base support,a base tube having a first end inserted into the cup, and a second endextending through the mounting collar and mateably engaging the femaleconnector.

In yet another embodiment of the present invention, a seating unitincludes a seat structure, a pedestal base, and a tablet assemblymounted between the seat structure and the base. The seat structureincludes a mounting bracket having a female connector. The pedestal baseincludes a gas cylinder having a top actuator button and a base mountingassembly. The base mounting assembly includes a receiver having a topmale connector, a bottom internal taper, and an internal buttonextender. The tablet assembly includes a support arm having a mountingcollar on one end of the support arm. The gas cylinder is inserted intothe bottom internal taper such that the button extender abuts the topactuator button, and the top male connector extends through the mountingcollar and mateably engages the female connector.

In another embodiment of the present invention, a seating unit includesa seat structure and a base. The base includes a top support and abottom pan. The top support includes three or more curved legs whichextend from a central hub. The pan is attached to the top support andincludes twice as many casters as the top support has legs. Both thelegs and casters are positioned equidistantly around a periphery of thepan, but the positioning of the legs is offset from the casters. Inparticular, the distance between a leg and an adjacent caster isapproximately equal to πD/4 x)−W/2, where D is the diameter of the pan,x is the number of legs, and W is the width of the leg.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other items and advantages of the present inventionwill be appreciated more fully from the following figures, where likereference characters designate like features in which:

FIG. 1 is a perspective view of a seating unit in a first embodiment,the seating unit including a tripod base and a tablet assembly;

FIG. 2 is a perspective view of a seating unit in a second embodiment,the seating unit including a tripod base and no tablet assembly;

FIG. 3 is a right side view of the seating unit of FIG. 1;

FIG. 4 is a right side view of the seating unit of FIG. 2;

FIG. 5 is a front view of the seating unit of FIG. 1;

FIG. 6 is a top view of the seating unit of FIG. 1;

FIG. 7 is a perspective view of a seating unit in a third embodiment,the seating unit including a pedestal base and a tablet assembly;

FIG. 8 is a perspective view of a seating unit in a fourth embodiment,the seating unit including a pedestal base and no tablet assembly;

FIG. 9 is a right side view of the seating unit of FIG. 7;

FIG. 10 is a right side view of the seating unit of FIG. 8;

FIG. 11 is an exploded top perspective view of the seating unit of FIG.1;

FIG. 12 is an exploded bottom perspective view of the seating unit ofFig.

FIG. 13 is an exploded view of a base to seat mounting assembly of theseating unit of FIG. 1;

FIG. 14 is an exploded cross-sectional view of the base to seat mountingassembly of FIG. 13;

FIG. 15 is a cross-sectional view of the base to seat mounting assemblyof

FIG. 16 is a bottom perspective view of a pivot assembly of the seatingunits of FIGS. 1 and 7;

FIG. 17 is an exploded bottom perspective view of the pivot assembly ofFIG. 16;

FIG. 17 A is an enlarged fragmentary view of a connecting portion of atablet mount of the pivot assembly of FIG. 17;

FIG. 18 is an exploded cross-sectional view of the tablet assembly ofFIGS. 1 and 7;

FIG. 19 is a cross-sectional view of the tablet assembly of FIGS. 1 and7;

FIG. 20A is a top view of the seating unit of FIG. 1 where the tabletassembly including a pivot assembly and a mounting assembly is in aright side, fully outward position;

FIG. 20B is a cross-sectional view of the pivot assembly of FIG. 20A,showing pivot assembly stops corresponding to the right side, fullyoutward position;

FIG. 20C is a cross-sectional view of the tablet mounting assembly ofFIG. 20A and a seating mounting rib, showing tablet mounting assemblystops corresponding to the right side, fully outward position;

FIG. 21A is a top view of the seating unit of FIG. 1 where the tabletassembly including a pivot assembly is in a right side, partially inwardposition;

FIG. 21B is a cross-sectional view of the pivot assembly of FIG. 21A,showing pivot assembly stops corresponding to the right side, partiallyinward position;

FIG. 22A is a top view of the seating unit of FIG. 1 where the tabletassembly including a pivot assembly and a mounting assembly is in aright side, fully inward position;

FIG. 22B is a cross-sectional view of the pivot assembly of FIG. 22A,showing pivot assembly stops corresponding to the right side, fullyinward position;

FIG. 23A is a top view of the seating unit of FIG. 1 where the tabletassembly including a pivot assembly and a mounting assembly is in afront, outward position;

FIG. 23B is a cross-sectional view of the pivot assembly of FIG. 23A,showing pivot assembly stops corresponding to the front, outwardposition;

FIG. 23C is a cross-sectional view of the tablet mounting assembly and aseating mounting rib of FIG. 23A, showing tablet mounting assembly stopscorresponding to the front, outward position;

FIG. 24A is a top view of the seating unit of FIG. 1 where the tabletassembly including a pivot assembly and a mounting assembly is in afront, partially inward position;

FIG. 24B is a cross-sectional view of the pivot assembly of FIG. 24A,showing pivot assembly stops corresponding to the front, partiallyinward position;

FIG. 25A is a top view of the seating unit of FIG. 1 where the tabletassembly including a pivot assembly and a mounting assembly is in afront, fully inward position;

FIG. 25B is a cross-sectional view of the pivot assembly of FIG. 25A,showing pivot assembly stops corresponding to the front, fully inwardposition;

FIG. 26 is a bottom perspective view of a seating structure and tabletmounting assembly of FIGS. 1 and 7;

FIG. 27 is an exploded view of a pedestal base and base to seat mountingassembly of the seating unit of FIG. 7;

FIG. 28 is an exploded view of the base to seat mounting assembly andseat structure of the seating unit of FIG. 7;

FIG. 29 is an exploded cross-sectional view of the base to seat mountingassembly of the seating unit of FIG. 28;

FIG. 30 is a cross-sectional view of the base to seat mounting assemblyof the seating unit of FIG. 7;

FIG. 31 is a perspective view of a base of the seating unit of FIGS.1-6;

FIG. 32 is an exploded perspective view of the base of FIG. 31;

FIG. 33 is a top view of the base of FIG. 31; and

FIG. 34 is a bottom view of the base of FIG. 31.

DETAILED DESCRIPTION OF THE INVENTION

For purposes of description herein, the terms “rear,” “front,”“vertical,” “horizontal,” and derivatives thereof shall relate to theinvention as oriented in FIG. 1. However, it is to be understood thatthe invention may assume various alternative orientations, except whereexpressly specified to the contrary. It is also to be understood thatthe specific devices illustrated in the attached drawings, and describedbelow are simply exemplary embodiments of the invented concepts. Hence,specific dimensions and other physical characteristics relating to theembodiments disclosed herein are not to be considered as limiting.

The present seating unit 10 includes a seat structure 12 and a base 14(FIGS. 2, 4, 8 and 10). The seat structure 12 and base 14 are connectedby a base to seat mounting assembly. The base to seat mounting assemblyincludes a base mounting assembly and a seat mounting bracket, bothdiscussed in detail below. Optionally, the seating unit 10 may include atablet assembly 16 (FIGS. 1, 3, 5-7 and 9). Referring to FIGS. 11-15,the tablet assembly 16 includes a tablet mounting assembly 18, a supportarm 20 attached to the mounting assembly at a first end 22, a pivotassembly 24 engaging the support arm at a second end 26, and a tablet 28attached to the pivot assembly. The mounting assembly 18 attaches to theseating unit 10 between and in-line with the seat structure 12 and base14. Referring to FIGS. 13-15 and 27-30, the mounting assembly 18includes a mounting collar 30 attached to the support arm first end 22,a bushing 32 or 32 a press fit into a bottom 34 of the mounting collar,and a pivot cover 36 nested over a top 38 of the mounting collar and thesupport arm 20. The pivot cover 36 preferably is constructed of plasticmaterial and includes a channel 40, a mousehole-shaped opening 42 andstop surfaces 44 and 46. The pivot cover 36 conceals stops and preventspinch points when the stops engage. The mousehole-shaped opening 42ensures that stop surfaces 44 and 46 contact the pivot cover 36 insteadof the first end 22 of the support arm 20. Where the pivot cover 36includes plastic, the mouse hole-shaped opening 42 replaces noisymetal-to-metal contact with a quieter metal-to-plastic contactcondition.

The tablet assembly 16 may turn freely on the base 14 through 360degrees of rotation. However, rotation of the support arm 20 isconstrained relative to the seat structure 12 to prevent the tablet 28from contacting the seat structure. The support arm 20 can rotateapproximately 110 degrees relative to the seat structure 12.Specifically, movement of the support arm 20 relative to the seatstructure 12 is restricted by stop surfaces 44 and 46 contacting stopson the seat structure. Rotation of the tablet assembly 16 relative tothe seat structure 12 is illustrated in FIGS. 20C and 23C. Contact andfriction between the tablet assembly 16 and the seat structure 12 aredesigned such that if a seated user swivels the seat structure relativeto the base 14, but does not touch the tablet assembly 16, the tablet 28will remain stationary relative to the base, until a stop is reached, atwhich point the tablet assembly will begin moving along with the seatstructure. The stops prevent contact between the tablet assembly and theseat structure which may damage both over time.

The pivot assembly 24 connects the tablet 28 to the support arm 20 andallows the tablet to rotate horizontally on the second end 26 of thesupport arm. Referring to FIGS. 16-19, the pivot assembly 24 includes atablet mount 48 secured to a bottom 50 of the tablet 28, a bushing 52press fit into the second end 26 of the support arm 20, and an innertube 54. The tablet mount 48 includes a connecting portion 56 having acentral passage 58 and a depression 60. The depression 60 includes edges62 and 64 which form stops. The bushing 52 includes a centralthroughbore 66, and a top annular flange 68. A top surface 70 of theannular flange 68 includes a rib 72 with bent ends 74 and 76 which formstop surfaces which restrict the relative motion of the tablet 28 on thesupport arm 20. Typically, rib 72 is made of a plastic material, so bentends 74 and 76 replace hard, noisy metal-to-metal contact with a quietermetal-toplastic contact condition. The top flange 68 also includes acutout 78 positioned parallel to the rib 72. The second end 26 of thesupport arm 20 includes a projection 80 corresponding to the cutout 78.The shapes of the rib 72, cutout 78 and projection 80 correspond to eachother and may be linear, angled or arcuate. However, in a preferredembodiment, the shapes of the rib 72, cutout 78 and projection 80 arearcuate.

To assemble the pivot assembly 24, the bushing 52 is press fit into thesecond end 26 of the support arm 20 with the projection 80 passingthrough the cutout 78 such that the rib 72 and projection are adjacentto each other. A lower end 82 of the inner tube 54 is inserted andsecured in the bushing throughbore 66, and an upper end 84 of the innertube 54 is inserted and secured in the tablet mount passage 58. When theinner tube 54 is inserted into the passage 58 of the tablet mountconnecting portion 56, the top surface 70 of the annular flange 68 abutsa bottom 86 of the connecting portion and the rib 72 and projection 80reside in the depression 60. When assembled, the bottom 86 of theconnecting portion 56 and the annular flange 68 work together to concealthe stops where edge 64 contacts bent end 76 and edge 62 contacts bentend 74, thereby preventing pinch points.

Rotation of the tablet 28 relative to the support arm 20 is illustratedin FIGS. 20A and B through 25A and B. Horizontal rotation of the tablet28 is restricted to prevent the tablet 28 from contacting the seatstructure 12, to allow a user to comfortably sit on and exit from thechair, and to ensure adequate stability of the seating unit 10.Regarding stability, horizontal outward rotation of the tablet 28 isrestricted to prevent tipping of the chair. When the tablet 28 isrotated outward and an object is placed on the tablet, the weight of theobject, W_(obj), produces a moment, M_(obj), that can tip the seatingunit 10 over if the center of the tablet extends beyond the base of theseating unit. The value of moment M_(obj) is equal to the weight of theobject, W_(obj), multiplied by the shortest horizontal distance,L_(obj), between the center of the weight, W_(obj), and the axis ofrotation, where the axis of rotation is a line drawn through thecenterlines of two casters 162 nearest to the object. For the seatingunit 10 to be stable, M_(obj) must be less than or equal to acounterbalancing moment, M_(su), formed by the weight of the seatingunit, W_(su), multiplied by the shortest horizontal distance L_(su) fromthe seating unit's center of mass to the axis of rotation. This isexpressed mathematically as M_(obj)≦M_(su) or (W_(obj)*L_(obj)) S(W_(su)*L_(su)). In a preferred embodiment, maximum outward rotation ofthe tablet 28 relative to the support arm 20 is restricted to an anglewhere the tablet 28 does not tip when an object weighing up to 25 poundsis placed onto the center of the tablet (Le., w, W_(obj)≦25 pounds).Specifically, maximum outward rotation of the tablet 28 is restricted toapproximately 60 degrees by bent end 74 contacting edge 62 (FIGS. 20A,20B, 23A, 23B) to prevent the seating unit 10 from tipping. Also, in apreferred embodiment, maximum inward rotation of the tablet 28 relativeto the support arm 20 is restricted to approximately 60 degrees by bentedge 76 contacting edge 64 (FIGS. 22A, 22B, 25A, 25B) to prevent thetablet from contacting the seat structure 12.

The tablet 28 is illustrated in FIG. 18 and includes a tray base 88attached to the tablet mount 48 and a skin 90 attached to the tray base.The tray base 88 is typically constructed of a strong structuralmaterial such as glass-filled nylon. The skin 90 can be molded from awide variety of materials, such as acrylonitrile butadiene styrene (A8S)or other plastic materials. Optionally, an insert 92 may be molded intothe skin 90. Suitable inserts 92 may be constructed of a high pressurelaminate (HPL) or thermoplastic polyurethane (TPU). To prevent rattlingand to dampen sound resonating through the tray base 88, an intermediatelayer 94 may be positioned between the tray base and skin 90. Typically,the intermediate layer 94 includes a nonwoven sheet. A thin layer ofsoft cellular foam or damping foil may also be used as the intermediatelayer.

The seat structure 12 rotates freely on the base 14 through 360 degreesof rotation and includes a backrest 96, a seat 98, armrests 100 and aseat mounting bracket 102 (FIGS. 12, 13, 26 and 28). Typically, thebackrest, seat and armrests are formed as a one-piece shell.Alternatively, the backrest, seat and armrests may be separate. Thebackrest and seat may also include upholstery. The armrests 100 extendupwardly and outwardly from a lower portion 104 of the backrest 96 toform a valley 106 between the armrest and the backrest. A backpack,purse, bag, or other article having a strap can be hung on an armrest100 by placing the strap into the valley 106 and around the armrest. Thearticle supported by the armrest is available for easy access by aseated user.

Referring to FIGS. 13 and 28, an underside 108 of the seat 98 includesmultiple protrusions 110 molded into and integral with the seat. Theprotrusions 110 include an over-molded boss insert 112 having a centralaperture 114. Although the seat 98 may include any number of protrusions110, preferably, there are four protrusions. Attached to protrusions 110is the mounting bracket 102 for connecting the seat structure 12 to thebase 14 and optionally to a tablet assembly 16. The mounting bracket 102can be any shape, but preferably the bracket is X-shaped and includes anaperture 116 near an end 118 of each leg 120 of the X. The mountingbracket 102 can be attached to the seat 98 by passing a fastener 122through the aperture 116 in the leg 120 and into a correspondingaperture 114 in a protrusion 110. Alternatively, the mounting bracket102 may be attached to the seat 98 using an adhesive or rivets. Themounting bracket 102 also includes a central female connector 124 and anannular rib 126 surrounding the female connector. As illustrated inFIGS. 12, 13 and 26, the height of the annular rib 126 is not uniform,but rather includes a first portion 128 having a greater height than asecond portion 130. The first and second portions 128, 130 are connectedby angled portions 132 and 134. Angled portions 132, 134 form stopsurfaces which restrict movement of the tablet assembly 16 relative tothe seat structure 12. In particular, movement of the support arm 20toward the rear of the seat structure 12 is restricted by stop surface44 contacting angled portion 132. Likewise, movement of the support arm20 toward the front of the seating structure 12 is restricted by stopsurface 46 contacting angled portion 134. (See FIGS. 20C and 23C).Referring to FIGS. 9, 10 and 27-30, for a seating unit 10 including apedestal base, the mounting bracket 102 may also include a lever 136.The lever 136 is used to activate an actuator button 138 of a verticallyadjustable gas cylinder 140.

The base 14 includes a base support 142 and a base mounting assembly 144(FIG. 11). As illustrated in FIGS. 1-6, 11, 12 and 31-34, the basesupport 142 may have three or more legs 146. In an alternativeembodiment, the base support may include a pedestal with radiallyextending legs 148, such as a five-star pedestal (FIGS. 7-10 and 27-30).

Referring to FIGS. 31 and 32, in one embodiment, the seating unit 10includes a base 14 having a tripod base support 150. The tripod basesupport 150 includes a top 152 attached to a bottom pan 154. The pan 154can be used to store a backpack, purse, bag, or other article. The top152 includes three curved legs 146 extending from a central hub 156 andattached to a bottom ring 158. A seated user can also use the pan 154 orbottom ring 158 as a footrest. Preferably, the bottom ring 158 isattached to legs 146 to minimize cost and maximize structural integrityof base 150. However, in an alternative embodiment, the bottom ring 158may be attached to the bottom pan 154. The bottom ring 158 includes aplurality of pintle mounts 160 for mounting casters 162 or glides. In apreferred embodiment, the legs 146 and pintle mounts 160 are positionedequidistantly around the bottom ring 158 (see FIGS. 33 and 34). Flankingthe pintle mounts 160 are fastening bosses 164. The bottom pan 154 canbe any shape, but preferably is circular. The pan 154 typically includesa series of holes 166. The series of holes 166 permits air flow throughthe pan 154 and allows liquids from stored articles or shoes which mayaccumulate to drain. Typically, the series of holes 166 is arranged in acircular pattern of small holes, however, any other pattern or hole sizecan be used. The bottom pan 154 also includes a plurality of apertures168 located equidistantly adjacent a periphery 170 of the pan. Theplurality of apertures 168 includes a central opening with a smallerhole on each side of the central opening. The position of the apertures168 corresponds to the position of the pintle mounts 160 and fasteningbosses 164. To assemble the base 14 including a tripod base support 150,the top 152 is positioned over the bottom pan 154 with the pintle mounts160 extending through the central hole of apertures 168. Fasteners 172pass through the two smaller holes of apertures 168 and engage thefastening bosses 164 to secure the pan to the top 152. Optionally, thetop 152 and bottom pan 154 may include clips (not shown) positionedbetween pintle mounts 160 and casters 162, respectively. The top clipsare releasably engaged to the bottom clips. The clips help maintaincontact between the top 152 and bottom pan 152 and prevent gaps betweenthem. Casters 162 or glides are inserted into the pintle mounts 160. Asthe seating unit 10 moves around, articles stored on the pan 154 remainwith the seating unit and are available for access by a seated user.

Typically, the tripod base support 150 includes six pintle mounts 160and casters 162, although more pintle mounts and casters can be used. Asnoted above, in a preferred embodiment, the pintle mounts 160 and legs146 are positioned equidistantly around the bottom ring 158 of the top152. When the tripod base support 150 includes six pintle mounts 160,each pintle mount is positioned approximately 60 degrees from adjacentmounts and each leg 146 is positioned approximately 120 degrees fromadjacent legs. To maximize stability of the seating unit 10 and minimizedeflection of the base pan 154, the pintle mounts 160 and casters 162are offset from the legs 146. It has been discovered that when at leastsome of the pintle mounts 160 and casters 162 line up with the legs 146,the structural integrity of the base 150 and the stability of theseating unit 10 is compromised. Specifically, where the pintle mounts160 and casters 162 are in-line with the legs 146, a user sitting on theseating unit 10 applies a load which is transferred to the casters belowthe legs. However, almost no load is transferred to the remainingcasters. An uneven load distribution can cause pintles and casters tobreak. Also, the in-line configuration may also compromise the stabilityof the seating unit and create potential safety issues for a seateduser. For example, if a user turns the seating unit 10 such that one ofthe legs 146 faces straight forward and an open section faces backward,and then leans back, the user can rock with the seating unit pivoting onthe two rear legs. The rear portions of the pan 154 and bottom ring 158flex excessively and the front casters 162 lift off the ground, causingthe seated user to tip backwards. Offset casters 162 and legs 146address both of these issues by distributing loads and stresses evenlyamong all casters and reducing the ability of a user to flex the pan 154and bottom ring 158 when leaning backwards. This is true whether thepintle mounts 160 and casters 162 are positioned equidistantly aroundthe bottom ring 158 or not. However, it has been discovered thatpreferably the number of casters 162 is 2 x, where x is the number oflegs 146, and the distance between a midpoint 174 of where the legattaches to the bottom ring 158 (Le., half the width, W, of the bottomof the leg) and adjacent casters is TTD/4 x, where D is the diameter ofthe pan 154. In other words, the distance from an edge of a leg 146 tothe nearest adjacent caster is TTD/4 x−W/2.

The base mounting assembly 144 components vary depending on the type ofbase support. The base mounting assembly 144 for a tripod base support150 is illustrated in FIGS. 13-15. In this embodiment, the base mountingassembly 144 includes a cup 176 with a flange 178 at a top end 180, abushing 182 press fit into the cup, and a base tube 184. The cup 176 isinserted into the central hub 156 and the flange 178 is secured to thebase top 152. A bottom end 186 of the base tube 184 is inserted throughthe bushing 182 and into the cup 176. The bushing 182 and bottom end 186of the base tube 184 are secured to a bottom 188 of the cup 176 with afastener and a series of washers and thrust bearings 190. Typically, thefastener is a mechanical fastener such as a shoulder bolt.

Referring to FIG. 15, to assemble the seating unit 10 including a base14 having a tripod base support 150 and a tablet assembly 16, a top end192 of the base tube 184 is inserted through the tablet mountingassembly 18 and mateably engages the female connector 124 of the seatmounting bracket 102. In this configuration, a bottom portion 194 of thetablet mounting assembly 18 resides in the base cup 176, and the annularrib 126 of the seat mounting bracket 102 resides in the channel 40 ofthe tablet mounting assembly pivot cover 36.

Referring to FIGS. 7-10, in an alternative embodiment, the seating unit10 includes a base 14 having a pedestal base support 196. One example ofa suitable pedestal base support is a five-star pedestal base supporthaving a vertically adjustable gas cylinder 140 and radially extendinglegs 148. Typically, the gas cylinder 140 is tapered and includes a topactivated actuator button 138. The base mounting assembly 144 for apedestal base support 196 including a tapered gas cylinder 140 isillustrated in FIGS. 27-30. In this embodiment, the base mountingassembly 144 includes a receiver 198 having a top 200 and a bottom 202,and a button extender 206. The receiver 198 is generally cylindrical andincludes a tapered male connector 208 at the top 200. The receiver 198also includes an internal taper 210 and an outer flange 212 at thebottom 202. The tapered gas cylinder 140 is accepted into the internaltaper 210 and the button extender 206 is inserted into the maleconnector 208.

Referring to FIG. 30, to assemble the seating unit 10 including apedestal base support 196 and a tablet assembly 16, receiver 198 of thebase mounting assembly is inserted into the bushing 32 a of the tabletassembly 16 such that the bottom 34 of the mounting collar is supportedby the receiver flange 212 and bushing, and the receiver extends throughthe pivot cover 36. In this configuration, the male connector 208including the button extender 206 of the receiver 198 extends past thetop of the bushing 32 a and mateably engages the seat mounting bracket102 female connector 124, and the annular rib 126 of the seat mountingbracket resides in the channel 40 of the tablet mounting assembly pivotcover 36. The button extender 206 abuts the lever 136. To verticallyadjust the height of the seating unit 10, a user engages the lever 136which depresses the button extender 206. In turn, the button extender206 depresses the gas cylinder actuator button 138 to provide verticaladjustment of the seating unit. Advantageously, the height of the tabletassembly is adjustable in tandem with the seat structure 12 when the gascylinder 140 is activated.

For a seating unit 10 having either a tripod base support 150 orpedestal base support 196, the pivot assembly 24 and base mountingassembly 144 advantageously cooperate to allow a seated user to pull thetablet 28 closer, or push it farther away, maintaining the front edge ofthe tablet perpendicular to the centerline of the seat, with minimalside-to-side displacement of the tablet. This cooperation between thepivot assembly 24 and base mounting assembly 144 allows users of varioussizes to comfortably use the tablet 28.

As illustrated in FIGS. 2, 4, 8 and 10, the seating unit 10 may beassembled without a tablet assembly 16. In particular, to assemble theseating unit 10 including a base 14 having a tripod base support 150,the base tube 184 is inserted into the seat mounting bracket 102, withthe top end 192 mateably engaging the female connector 124. Similarly,to assemble the seating unit 10 including a base 14 having a pedestalbase support 196, the receiver 198 is inserted into the seat mountingbracket 102, with the male connector 208 including the button extender206 mateably engaging the female connector 124. A seating unit 10 notincluding a tablet assembly 16 may also include an aesthetic coverpositioned between the base mounting assembly 144 and seat mountingbracket 102. Alternatively, a seating unit 10 without a tablet assembly16 may be constructed by omitting the receiver 198, the button extender206 and any aesthetic covers. The tapered top of the gas cylinder 140would mateably engage the female connector 124 of the mounting bracket102, and the lever 136 would directly activate top activator button 138.

The seating unit 10 is easy to ship in a ready-to-assemble form with theseat structure 12, base 14 and optional tablet assembly 16 separate.This saves space and reduces packaging costs, while minimizing finalassembly labor and complexity. Final assembly of the seating unit 10 isaccomplished by optionally placing the tablet assembly 16 onto the base14 and then placing the seat structure 12 onto the base and applyingdownward pressure. The final assembly processes disclosed above requireno tools or small parts or hardware items which can be lost.

The invention claimed is:
 1. A seating assembly comprising: a basecomprising: a plurality of casters; a bottom ring supported by thecasters; a pan supported by the bottom ring and adapted to supportarticles above the floor surface; a central hub forming an upwardlyopening cavity; a plurality of legs extending outward and downward fromthe central hub to the bottom ring and wherein the locations at whichthe legs connect to the bottom ring are offset from the positions of thecasters; a one-piece molded seat shell comprising: a seat member havingan undersurface and four protrusions molded into and extending downwardfrom the undersurface of the seat member, each protrusion adapted toreceive a fastener; a backrest; and first and second armrests; amounting bracket forming four apertures and including a female connectorand at least one rib member that extends downward adjacent the femaleconnector, the at least one rib member including end edges that formsfirst and second stop surfaces, the mounting bracket attached to thebottom of the seat by passing fasteners through the apertures and intothe protrusions; a support arm having first and second ends; a mountingassembly including: a cup member received in the upwardly opening cavityformed by the central hub, the cup member forming an upwardly openingcavity; a base tube having upper and lower ends, the lower end receivedin the upwardly opening cavity formed by the cup member and the upperend engaging the female connector; a annular mounting collar supportedby the cup member for rotation about a substantially vertical axis, thesupport arm connected to the mounting collar and extending to one sideof an external surface of the mounting collar; and a pivot cover formingan upwardly opening annular channel and an inverted U-shaped opening,the pivot cover attached to the mounting collar with the first end ofthe support arm extending through the inverted U-shaped opening and theat least one rib member received within the annular channel; and atablet supported at the second end of the support arm.
 2. The assemblyof claim 1 wherein the pivot cover includes upper and lower ends andwherein the annular channel extends into the upper end of the pivotcover.
 3. The assembly of claim 2 wherein the inverted U-shaped openingis formed in the lower end of the pivot cover and opens downwardly. 4.The assembly of claim 3 wherein the pivot cover separates the first andsecond stop surfaces from the support arm.
 5. The assembly of claim 4,wherein the central hub includes a substantially planar surface thatsurrounds the upwardly opening cavity formed by the central hub, the cupmember including a laterally extending flange that is supported by theplanar surface.
 6. The assembly of claim 5 wherein the mounting collarincludes a lower end that extends below the first end of the supportarm, the lower end of the mounting collar received within the cupmember.
 7. The assembly of claim 6 wherein the cup member includes acylindrical external wall member that forms the upwardly opening cavityand an internal tube member spaced from the external wall member, theinternal tube member forming an upwardly opening passage, the lower endof the base tube received in the upwardly opening passage and the lowerend of the mounting collar received in the space between the externalwall member and the internal tube member.
 8. The assembly of claim 7wherein a first bushing is located between an internal surface of themounting collar and the internal tube member and a second bushing islocated between an external surface of the base tube and the internaltube member.
 9. The assembly of claim 1 wherein the mounting bracketfurther comprises four outwardly extending portions and wherein one ofthe four apertures is formed near a distal end of each segment.
 10. Theassembly of claim 1 wherein the pan has a general shape and forms aplurality of holes and wherein each hole has a shape that issubstantially similar to the general shape of the pan.
 11. The assemblyof claim 10 wherein the holes formed by the pan are arranged in apattern that has a general shape and wherein the general shape formed bythe holes is substantially similar to the general shape formed by thepan.
 12. The assembly of claim 11 wherein the bottom ring forms acontinuous internal surface that extends substantially vertically from aperipheral portion of a top surface of the pan.
 13. The assembly ofclaim 12 wherein the top surface of the pan is concave upward.
 14. Theassembly of claim 1 wherein the bottom ring is integrally formed withthe legs and central hub.
 15. The assembly of claim 1 wherein the seatmember is dimensioned and located to be within a columnar volume thatextends upward from and above the pan.
 16. The assembly of claim 15wherein the mounting bracket further comprises four portions that extendoutwardly from a central portion and wherein an aperture is formedproximate a distal end of each of the four portions that extendoutwardly and wherein two of the segments are longer than the other twosegments.
 17. The assembly of claim 16 wherein the mounting bracket issubstantially X-shaped.
 18. The assembly of claim 15 wherein thebackrest includes a rear edge that resides outside the columnar volumethat extends upward from the pan.
 19. The assembly of claim 1 whereinthe mounting bracket includes an undersurface and the central hubincludes a top surface and wherein the pivot cover extends from theundersurface of the mounting bracket to the top surface of the centralhub.
 20. The assembly of claim 1 wherein the mounting collar includes anupper portion and a lower portion and wherein the upper portion extendsinto and is substantially surrounded by the pivot cover and the lowerportion extends into and is substantially surrounded by the cup member.21. The assembly of claim 1 wherein the first and second stop surfacesare located within an annular path that surrounds the female connector,the first end of the support arm passing through the annular pathbetween the first and second stop surfaces.
 22. The assembly of claim 1wherein the pan forms a plurality of openings that are spaced about aperipheral portion of the pan, the bottom ring having an undersurface, aplurality of pintle mounts extending downward from the undersurface ofthe bottom ring, the bottom ring mounted to the pan with the bottom ringcontacting the peripheral portion of the pan and each pintle mountextending through one of the openings formed in the pan, a separatecaster mounted to each of the pintle mounts.
 23. The assembly of claim22 wherein the pan includes a central portion within the peripheralportion, each opening located at a height above the bottom surface ofthe central portion.
 24. A seating assembly comprising: (a) a baseincluding: (i) a pan member having a top surface, a bottom surface, anouter edge, a central portion and a peripheral portion that surroundsthe central portion and that is adjacent the outer edge, the outer edgeforming a shape of the pan member, the top surface concave upward withthe peripheral portion at a height above a height of the centralportion, the pan member forming a plurality of openings that are spacedabout the peripheral portion, each opening located at a height above thebottom surface of the central portion; (ii) a bottom ring forming a loophaving a shape that is substantially similar to the shape of the panmember and having an undersurface, a plurality of pintle mountsextending downward from the undersurface of the bottom ring, the bottomring mounted to the top surface of the pan member with the bottom ringcontacting the peripheral portion of the pan member and each pintlemount extending through one of the openings formed in the pan member;(iii) a central hub forming a substantially flat top surface and formingan opening in the top surface for receiving a lower portion of amounting assembly; (iv) a plurality of leg members that extend upwardand inward from spaced apart locations of the bottom ring to the centralhub to support the central hub above the central portion of the panmember; and (v) a plurality of casters, a separate caster mounted toeach of the pintle mounts; (b) a one-piece molded seat shell comprising:(i) a seat member having an undersurface and a plurality of protrusionsmolded into and extending downward from the undersurface of the seatmember, each protrusion adapted to receive a fastener; (ii) a backrest;and (iii) first and second armrests; (c) a mounting bracket including acentral portion and four extending portions that extend outwardly fromthe central portion to distal ends, the central portion forming a femaleconnector and each extending portion forming an aperture proximate thedistal end of the extending portion, wherein the mounting bracket isattached to the undersurface of the seat member by passing fastenersthrough the apertures into the protrusions; and (d) a mounting assemblyincluding: (i) a cup member received in the upwardly opening cavityformed by the central hub, the cup member forming an upwardly openingcavity; and (ii) a base tube having upper and lower ends, the lower endreceived in the upwardly opening cavity formed by the cup member and theupper end engaging the female connector to support the seat shell abovethe base.
 25. The assembly of claim 24 wherein the leg members areconnected to the bottom ring at locations that are offset from thelocations at which the pintle mounts extend and the seat member isdimensioned and located to be within a columnar volume that extendsupward from and above the pan.